Solvent and method for removing waxy deposits



United States Patent 3,193,499 SQLVENT AND METHQD FQR REMQVlNG WAXY DllPtlSli'iS Donald E. Qarr, Bartlesville, Gilda assignor to Phillips Petroleum tlompany, a corporation of Delaware No Drawing. Filed Get. 3, 1961, Ser. No. 142,490 6 Claims. (Cl. 252--8.55)

This invention relates to a novel solvent composition. It also relates to the use of the novel solvent composition for the removal and/or prevention of deposits and plugs of waxy material found in petroleum pipelines, oil-tubing and underground formations which are produced. In one of its aspects, the invention relates to a composition comprising a calcium petroleum sulfonate in admixture with a highly branched parafiinic hydrocarbon. In another of its aspects, the invention relates to the removal of waxy material from various places such as pipelines, oil-well tubing and producing underground formations by contacting the same with a composition as herein described.

When petroleum is transported through pipelines, well tubing or through porous underground formations, changes in conditions such as pressure, temperature, oxidationreduction potential, concentration, and the like, occur which cause the previously stable petroleum mixture to become unstable and to deposit on the conduit walls or in the pores of the formation and, by prior art means, can only be redispersed by heat and expensive solvents. Solvents which have been described in the literature as suitable are generally not petroleumderived and, therefore, are not always available to the petroleum producer, or cannot be procured by him at a price which permits economic cleaning of the pipeline, well casing or reservoir.

When the deposit is formed, a characteristic of the deposit is to cling tenaciously to the inorganic material upon which it is deposited. On attempting to remove the deposits by materials which are well known to wet the surface of inorganic materials (other than strong mineral acids), the response is nil or so slow that these methods have generally been abandoned. It is believed that the deposits tend to protect the surface of the inorganic ma terial on which it is deposited.

Hot solvents have been reasonably effective in removing deposits of a parafiinic nature from producing oil wells, but the cost of applying the method to marginal producing units have been high based on the amount of petroleum produced between treatments. The solvents utilized have in many instances enhanced the deposition effects by providing an ideal surface upon which the new deposits can form. Attempts to utilize the hot solvent method to open up plugged formations has, except in acidizing, proven rather costly when the amount of recovered petroleum is balanced against solvent losses, amortization and man-power necessary for its recovery.

It has now been found that a solvent composition with an increased rate of penetration is obtained when calcium petroleum sulfonates (CPS), for example, made in accord.- ance with the process set forth in US. Patent 2,884,445, issued April 28,1959, by William N. Axe and James T. Gragson, and having a sulfonate content in the range of about 3.5 to about 5.2 percent, ash in the range about 4.5 to about 8.5 weight percent with a total base number above about 7 and a solids of less than about .05 weight percent and a viscosity in the range 1500 to 2200 SSU at 210 F. are admixed with a branched chain paraifinic fraction, for example, as obtained from the acid-catalyzed alkylation of isoparaflins with olefins and having an initial ASTM (D86-52) distillation temperature in the range of about 335 to 430 F., a 50 percent point in the range 355 to 450 F., and an end point in the range 380-475 F., a

3,l3,49 Patented July 6, 1965 specific gravity (ASTM D287-52) in the range 0.75 to 0.78 at 60 F., a kauri-butanol value (ASTM Dll33-50T) in the range 21 to 27 ml. and an aniline point of 182 to F. (ASTM D1012-5l) will yield an improved general cleaning agent for pipelines, well casings and plugged underground formations.

Generally, it has been found that various combinations of calcium petroleum sulfonates, depending upon their character, and isoparaflinic hydrocarbons, especially as derived from acid-catalyzed alkylation of isoparafiins with olefins, more particularly from the HF-acid-catalyzed al kylation of isoparafiins with olefins, as presently practiced in the production of motor fuel or motor fuel components, will give good solvent action or good action upon, say, a formation or pipeline which later can be cleaned with still a further solvent material.

It is an object of the invention to provide a petroleum derived solvent system for the removal of petroleum derived deposits from means and strata utilized in the pro duction and transportation of petroleum.

It is another object of the invention to provide a solvent for petroleum derived deposits which readily wets inorganic surfaces covered by a parafiinic material.

It is yet another object of the invention to provide a solvent combination in which the petroleum derived deposits are readily dispersed after separation from the surface on which the deposit was extant.

It is a further object of the invention to increase the rate of penetration of solvent utilized in the removal of plugs of petroleum derived materials from porous strata, pipelines, etc.

According to the present invention, an improved solvent for removing deposits, especially parafiinic deposits, from oil Wells, pipelines, and porous strata is provided comprising a calcium petroleum sulfonate in combination with a branched chain parafiinic hydrocarbon. While the composition of the present invention will lie within the compositions established by the ranges of properties given herein for now-preferred results, it is clear that one skilled in the art possessed of this disclosure and having studied the same, can, depending upon the calcium petroleum sulfonate and the isoparafiinic fraction selected, obtain combinations for mixtures which will be suitable for his purposes upon mere routine testing.

Consideration of the mechanism by which the invention appears to work well leads to the belief that there is a cooperative effort between the two materials in the composition of the invention. Thus, it appears that the branched chain parafiins, which cover a large surface due to their extensive surface covering ability or afiinity and the tendency of calcium petroleum sulfonate to disperse materials or break down surface tension, coact together to give an action which causes the wax deposit to break loose from the surface on which they are formed.

A casing or porous underground formation which has been cleaned by the method of this invention which employs the composition of this invention remains free of wax for a longer period of time than when cleaned by methods heretofore used. It is unknown exactly why this should be true, but it is probably true that the dispersing action of the CPS in the thin film of hydrocarbon preferentially wetting the inorganic surface is responsible for this improvement.

It is within the scope of the invention, as earlier suggested, to use the preferred solvent pair of the invention during a pre-treatment period to open up or to considerably unplug, or sufliciently clean, an area or formation, and then, after recovering as much of the cleaning agent as possible, follow with a usually used solvent and usual treatment which then readily dissolves the loosened wax in a short time, probably because of the dispersing action of the CPS, earlier noted.

The following examples are representative of the operation of the invention and are based upon actual operations in the field:

Example 1 The Sin-Harrah in the West Pampa repressure area in the Texas Panhandle gives excessive pumping trouble because of flaky paraffin which plugs the pores of the reservoir and sticks to sucker rods. Intermittent treatment with hydrocarbons having high aromatic content or with kerosene and moth balls, and the like, has been more or less effective, but the production rate has declined from an initial rate of 29 barrels per day to the present 6-barrel rate although a normal projection indicates that the well should be producing in the neighborhood of barrels per day. Because of this abnormal decline, an electric heater was evaluated capable of raising the forma tion temperature from the present 160 F. to a temperature above the paraffin precipitation temperature and somewhere in the neighborhood of 200 to 250 F. The evaluation showed that such a project would be impractical because the well produces only 1 barrel of water per day. The solution of this invention comprising Soltrol, which is a heavy alkylate from the acid alkylation of isobutane with an olefin having 4 carbon atoms to the molecule and calcium petroleum sulfonate in the ratio of 2 volumes of calcium petroleum sulfonate per hundred volumes of Soltrol, when passed through a heater located at the surface of the well capable of heating the mixture to about 350 F. before injection increases the production to around 15 barrels per day. The deposited calcium petroleum sulfonate Will tend to inhibit the paraffin laydown in the reservoir and provide for freer movement of the sucker rod during the subsequent pumping operations.

Example 11 The Elbertine No. 2 in Wise County, Central Texas, was pumping 9 barrels of oil and 24M cubic feet of gas from 5,648 feet. On attempting to pull the rods preparatory to deepening the well, the rods were found to be stuck with parafiin. A mixture of 25 gallons of Soltrol (a heavy alkylate from acid akylation of an isoparafiin with an olefin) and 0.5 gallon of calcium petroleum sulfonate, when passed through the coils of a surface-1ocated heater (temperature about 275 F.), is effective on being dumped into the well in loosening the rods in about 2 hours whereas kerosene with moth balls (a much favored prior art method) requires about 4 hours to do the job under similar conditions.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, and the appended claims to the invention, the essence of which is that a calcium petroleum sulfonate and an isoparaffinic hydrocarbon, more especially as derived from the acid-catalyzed, more preferably HF-catalyzed, alkylation of an isoparaffin with an olefin, have been found to be a very good solvent pair for cleaning of waxy materials from surfaces where these may be found and that a method for cleaning pipelines, oil wells and earth formations containing waxy deposits, or tending to form the same, has also been set forth, as described.

I claim:

1. A composition, suitable for removing waxy deposits, consisting essentially of an isoparaffinic hydrocarbon liquid containing substantially only isoparaffins, said liquid boiling in the range of 335475 F., and a small amount of calcium petroleum sulfonate.

2. A composition consisting essentially of a calcium petroleum sulfonate having a sulfonate content in the range 3.5 to 5.2 percent, and ash in the range 4.5 to 8.5 weight percent, total base number above 7, solids less than 0.05 weight percent, a viscosity in the range 1500 to 2200 SSU at 210 F., in combination in a small amount with a branched chain paraffinic fraction containing substantially only isoparaffins having an initial ASTM (D86 52) distillation temperature in the range 335 to 430 F., a 50 percent point in the range 355 to 450 F. and an end point in the range 380-475 F., specific gravity (ASTM D287-52) in the range 0.75 to 0.78 at 60 F., a kauributanol value (ASTM D1133-50T), in the range 21 to 27 ml. and an aniline point of about 182 to 195 F. (ASTM D101251).

3. A composition suitable for removing waxy deposits from oil wells and oil formations consisting essentially of a small amount of a calcium petroleum sulfonate having a sulfonate content in the range 3.5 to 5.2 percent in an isoparafiinic hydrocarbon derived from acid-catalyzed alkylation of an isoparafiin with an olefin and having a distillation temperature in the range 335430 F.

4. A method for cleaning waxy material from oil Well reservoir pores and pipe lines associated therewith which comprises subjecting the same to the action of a composition consisting essentially of a small amount of calcium petroleum sulfonate in an isoparafiinic hydrocarbon liquid containing substantially only isoparatfins and boiling in the range of 335-475" F.

5. A composition suitable for removing waxy deposits from the oil wells consisting essentially of a heavy akylate obtained in the acid alkylation of isobutane with an olefin having 4 carbon atoms to the molecule and calcium petroleum sulfonate in the ratio of approximately two volumes of calcium petroleum sulfonate per volumes of said alkylate.

6. A method of cleaning waxy material from surfaces in an oil well which comprises subjecting the same to the action of a composition consisting essentially of an isoparafiinic hydrocarbon liquid obtained by the acid alkylation of isobutane with an olefin having 4 carbon atoms to the molecule and calcium petroleum sulfonate in an approximate ratio of two volumes of calcium petroleum sulfonate per 100 volumes of alkylate.

References Cited by the Examiner UNITED STATES PATENTS 2,358,665 9/44 Sharpiro i 252-8.55 2,816,073 12/57 Stratton 252--8.5 2,833,711 5/58 Arnold 2528.55 2,884,445 4/59 Axe et al. I 25233 2,937,112 5/60 Boyer 252-455 2,970,958 2/61 Shapiro 2528.55 3,105,810 10/63 Miller et al 2528.3

JULIUS GREENWALD, Primary Examiner. 

1. A COMPOSITION, SUITABLE FOR REMOVING WAXY DEPOSITS, CONSISTING ESSENTIALLY OF AN ISOPARAFFINIC HYDROCARBON LIQUID CONTAINING SUBSTANTIALLY ONLY IOSPARAFFINS, SAID LIQUID BOILING IN THE RANGE OF 335-475*F., AND A SMALL AMOUNT OF CALCIUM PETROLEUM SULFONATE. 